Adipocytokines and aging: adiponectin and leptin.

ABSTRACT

Adipose tissue is an active metabolic organ secreting adipocytokines which are involved in the energy homeostasis and regulation of glucose and lipid metabolism. Aging is associated with fat redistribution, which is characterized by loss of peripheral subcutaneous fat and accumulation of visceral fat. Visceral adipose tissue is more involved in the developement of metabolic diseases than subcutaneous adipose tissue. Aging also alters the function, proliferation, size, and number of adipose cells which leads to alterations in the secretion, synthesis and function of the adipocytokines. Adiponectin is an insulin sensitizing, anti-inflammatory, and antiathoregenic adipokine. Centarians have higher adiponectin levels associated with longevity. However, in older individuals ­ age 65 or more ­ adiponectin is associated with higher mortality. Dysregulation of adiponectin in older individuals may be due to loss of function of circulating adiponectin or a response to increased inflammatory process. Longitidunal increase in adiponectin levels 5with aging rather than genetically high adiponectin levels may translate to increased mortality in older patients. The adipocytokine leptin is traditionally viewed as a product of adipocytes that can exert endocrine effects. There have been conflicting reports of not only the effects of aging on leptin, but also the effects of leptin on age-related diseases including sarcopenia, Alzheimer's disease and cardiovascular diseases. Aging is also associated with resistance to leptin and/or to a decrease of receptors for this hormone. In this review, we briefly discuss the role of two major adipocytokines adiponectin and leptin in the aging process and age-related diseases.